Pointable optical transceivers for free space optical communication

ABSTRACT

Optical transceivers include a diffractive optical element (DOE) attached to a surface of a prism or other optical support. The DOE is configured to direct an input optical signal to a planar or curved reflective surface, or receive an output optical signal from the planar or curved reflective surface at angles greater than a critical angle in the prism. In some examples, the optical support includes one or more curved reflective surfaces and the DOE is a hologram. Such optical transceivers include a reflective surface that is rotatable with respect to the DOE, or with respect to a selected communication direction and the DOE for selection of a transmission or reception direction. The optical supports of such optical transceivers can be mounted to a window, and include a reflective region configured to total internally reflect optical signals. Selection of a communication direction is based on a rotation of the rotatable reflective surface.

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional PatentApplication 60/432,197, filed Dec. 9, 2002, and is acontinuation-in-part of U.S. patent application Ser. No. 10/020,518,filed Dec. 14, 2001, both of which are incorporated herein by reference.

TECHNICAL FIELD

[0002] The invention pertains to methods and apparatus for free spaceoptical communication.

BACKGROUND

[0003] While guided wave optical systems have become commonplace intelecommunications, such systems exhibit several practical limitations.Installation of such systems in existing buildings can be disruptive andlabor intensive, and in some cases cannot be economically configured toreach all building areas for which optical communication services aredesired. Communication applications between two or more buildings orother locations typically require underground installation of opticalcables in existing utility tunnels or burial in newly dug trenches. Suchinstallations can be slow and expensive. In addition, reconfiguration ofa guided wave communication system can be difficult as additionaloptical fiber or other waveguide must be installed to reach any newlyselected locations. As a result, an installed communication system canrequire expensive upgrades.

[0004] Free space optical communication systems do not exhibit thelimitations associated with the installation and maintenance of guidedwave optical communication systems. Such systems include opticaltransmitters and receivers that are configured to deliver and receiveoptical signals propagating in free space, and waveguides are not neededto connect the transmitter and receiver. In addition, such transmittersand receivers can be portable and readily adapted to a user's varyingcommunication requirements.

[0005] While free space optical communication systems have numerousadvantages, such systems typically have several drawbacks. Transmitterand receiver locations can be easily changed, but a transmitter and anassociated receiver must be located within a line of sight and selectionof a particular transmission or reception direction requires carefulalignment. Transceivers are also subject to mechanical disturbances thatcan degrade an existing alignment because transceivers are frequentlyplaced in exposed locations. For these reasons, improved free spaceoptical communication systems, methods, and apparatus are needed.

SUMMARY

[0006] Free space optical systems can use optical transceivers totransmit and receive optical signals. Optical transceivers can beconfigured to receive optical signals from a source such as a modulatedlaser diode or other source, and process the optical signal for freespace transmission. Such transceivers can also be configured to receiveoptical signals propagating in free space and to process such signalsfor delivery to an optical detection system that includes an opticaldetector such as a photodiode or avalanche photodiode. In representativeexamples, optical transceivers comprise a diffractive optical element(DOE) configured to receive an input optical beam. A reflective surfaceis configured to receive at least a portion of the input optical beamfrom the DOE and direct the portion to an optical detector. A mount isprovided for the reflective surface and is configured to rotate thereflective surface with respect to the DOE and thereby select anorientation of the reflective surface. The orientation of the reflectivesurface can be associated with, for example, reception of the inputoptical beam from a selected direction or transmission to a selecteddirection.

[0007] In representative examples, optical transceivers comprise adiffractive optical element (DOE) configured to transmit an inputoptical beam. A reflective surface is configured to receive thetransmitted optical beam from the DOE and direct a reflected opticalbeam to the DOE. A mount is configured to rotate the reflective surfaceso that the DOE diffracts at least a portion of the reflected opticalbeam to an optical detector. According to additional representativeexamples, optical transceivers comprise an index-matching materialsituated at the reflective surface, and extending from the reflectivesurface to the DOE. In other examples, transceivers include an opticalsupport having a first surface configured to receive the portion of theinput optical beam reflected by the reflective surface and to direct theportion to an output surface. In further examples, the DOE is configuredto diffract at least a portion of the optical beam received from thereflective surface to an output surface.

[0008] Optical transmitters comprise a diffractive optical element (DOE)configured to receive an output optical beam and a reflective opticalelement having a reflective surface configured to receive at least aportion of the output optical beam from the DOE and direct the portionto a recipient. A mount is configured to rotate the reflective opticalelement and select an orientation of the reflective surface, wherein theorientation of the reflective surface is associated with selection of atransmission direction. In other examples, optical transmitters comprisean index-matching material situated at the reflective surface andextending to the DOE. According to other representative examples,optical transmitters further comprise an optical support having a firstsurface configured to direct at least a portion of the output opticalbeam to the DOE. In further examples, the DOE is configured to diffractat least a portion of the output optical beam received from the firstsurface of the optical support to the reflective surface.

[0009] Optical transceivers comprise a diffractive optical element (DOE)and a reflective surface configured to receive an optical beam from theDOE and direct a reflected portion to the DOE. The reflective surface isrotatable with respect to the DOE for selection of, for example, acommunication direction. According to representative examples, the DOEis bonded to an optical support and is configured to direct the opticalbeam to an output surface of the optical support based on a wavelengthassociated with the optical beam. In additional examples, the opticalsupport includes a surface configured to communicate the optical beambetween the DOE and the output surface of the optical support. Inadditional representative embodiments, the surface of the opticalsupport is configured to communicate the optical beam between the DOEand the output surface by total internal reflection. In other examples,a communication direction is selectable based on a rotation angle of thereflective surface with respect to the DOE, or a rotation angle of thereflective surface with respect to the DOE and the output surface.

[0010] Optical transceivers comprise an optical support having a firstsurface configured to be situated adjacent a window, a second surface,and a coupling surface. A diffractive optical element (DOE) is situatedadjacent the second surface. A reflective optical surface and an opticalmount that is adjustable to select an orientation of the reflectiveoptical surface with respect to that DOE are provided so that the DOEand the reflective optical surface direct a light flux received from thefirst surface to the coupling surface, or direct a light flux from thecoupling surface to the first surface. In other examples, the secondsurface comprises a reflective region configured to direct a light fluxto the coupling surface or to the DOE. In some examples, the reflectiveregion includes a reflective coating or is situated to provide totalinternal reflection. In other representative examples, networks compriseat least two computer devices, and at least two such opticaltransceivers configured to interconnect the at least two computerdevices.

[0011] Communication methods comprise receiving an optical signal beamand directing the optical signal beam to a diffractive optical element(DOE). At least a portion of the optical signal beam received from theDOE is reflected back to the DOE. The DOE diffracts a portion of theoptical signal beam received from the reflective surface to an opticaldetector. According to representative examples, a communicationdirection is selected based on a rotation angle of the reflectivesurface with respect to the DOE. In other representative examples, thestep of selecting a communication direction includes adjusting anorientation angle of the reflective optical surface with respect to thecommunication direction.

[0012] Methods of processing an optical signal comprise directing theoptical signal to a diffractive optical element (DOE), receiving theoptical signal from the DOE, and reflecting the optical signal back tothe DOE. At least a portion of the optical signal reflected to the DOEis diffracted to a surface of an optical support so that the portionpropagates in the optical support at an angle greater than a criticalangle with respect to the surface. According to other representativeexamples, the optical signal is directed to a surface of the opticalsupport having optical power that is based on a surface curvature.

[0013] These and other features and advantages are set forth below withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a block diagram of a free space optical communicationsystem illustrating communication between two buildings.

[0015]FIG. 2 is a schematic diagram of an optical transceiver configuredfor use in a free space optical communication system.

[0016]FIG. 3 is a schematic diagram of an optical transceiver configuredfor use in a free space optical communication system.

[0017]FIG. 4 is a schematic diagram of an optical transceiver configuredfor use in a free space optical communication system.

[0018]FIG. 5 is a schematic diagram of an optical transceiver configuredfor use in a free space optical communication system. FIG. 6 is aschematic diagram of an optical transceiver configured for use in a freespace optical communication system.

[0019]FIG. 7 is a schematic diagram of an optical transceiver configuredfor use in a free space optical communication system.

[0020]FIG. 8 is a schematic diagram of an arrangement for recording ahologram for use in an optical transceiver.

[0021]FIG. 9 is a diagram illustrating an optical transceiver configuredfor mounting to a window.

[0022]FIGS. 10A-10B are schematic diagrams of optical mounting andalignment mechanisms for mounting an optical transceiver to a window.

[0023]FIG. 11 is a schematic diagram of an optical transceiver thatincludes a mirror that directs an optical signal to a hologram or otherdiffractive element.

[0024]FIG. 12 is a schematic diagram of an optical transceiver thatincludes a reflection hologram.

[0025]FIG. 13 is a schematic diagram of an optical transceiver thatincludes a hologram situated on a curved surface.

[0026]FIG. 14 is a schematic diagram of an optical transceiver thatincludes first and second holograms that direct an optical beam toward acoupling surface and converge, the optical beam at the coupling service,respectively.

[0027]FIGS. 15-16 are perspective views of optical transceiversconfigured to transmit and receive spatially separated optical signals.

[0028]FIG. 17 is a sectional view of an optical transceiver situated ata dual pane window and that is adjustable using a gimbal mount.

[0029]FIG. 18 is a sectional view of an optical transceiver situated ata dual pane window that includes a curved mirror that is adjustableusing a gimbal mount.

[0030]FIG. 19 is a schematic diagram of an optical transceiver thatincludes a reflection hologram.

[0031]FIG. 20 is a schematic diagram of an optical transceiverconfigured for use in a free space optical communication system.

[0032]FIG. 21 is a schematic diagram of an optical transceiver thatincludes an adjustable reflector.

DETAILED DESCRIPTION

[0033] With reference to FIG. 1, a communication system is configured totransmit data, voice, or other information between buildings 102, 104.An optical transceiver 106 is situated at or near a window 107 and isconfigured to transmit optical signals produced by an opticaltransmitter/receiver module 108 to the building 104. The opticaltransceiver 106 is also configured to receive optical signals from thebuilding 104 and direct the received optical signals to the opticaltransmitter/receiver module 108. The received optical signals areconverted to electrical signals at the transmitter/receiver module 108or can be deliver by an optical fiber or other optical apparatus to aserver 110 that includes electrical-to-optical and/oroptical-to-electrical conversion circuitry. The associated electricalsignal is then processed by the server 110 or other computer or networkelement.

[0034] An optical transceiver 112 is similarly configured at thebuilding 104 for communication with the building 102. The opticaltransceiver 112 is situated at or near a window 113 and is configured totransmit optical signals to and receive optical signals from the opticaltransceiver 106. Received optical signals are directed to atransmitter/receiver module 114 that is in communication with a server116 or other computer or network element. The transmitter/receivermodule 114 can include optical-to-electrical converters or can beconfigured to transmit optical signals to and from optical-to-electricalconversion circuitry located at, for example, the server 116.

[0035] Representative optical transceiver configurations are illustratedschematically in FIGS. 2-7, 9, and 11-13. For convenience, surfacecurvatures are shown for purposes of illustration only and it will beapparent how surface curvatures can be selected and configured. Inaddition, multiple surfaces are shown for producing optical beamconvergence and focusing, but surfaces can also be selected to producebeam divergence and defocusing as well as aberration correction andvarious telescope configurations can be adapted for such use.Descriptions of example transceiver configurations are provided withreference to transceiver use as a transmitter, receiver, or both. Theexample transceivers can generally be used for both applications and forconvenience, are described with reference to transmitter or receiver useonly. Optical surfaces through which optical signals are received froman optical source for transmission, or delivered to an optical detectionsystem are referred to as coupling surfaces. Examples are described withreference to holograms, but other diffractive optical elements can beused. In some examples, some surfaces are tilted with respect to others,but nevertheless remain approximately parallel. For convenience, tilted,substantially parallel surfaces are defined as surfaces that are tiltedat angles of less than about 20 degrees with respect to each other.

[0036] In some examples, optical signals propagate within an opticalsupport or a prism at angles with respect to one or more surfaces suchthat the optical signals are totally internally reflected. As usedherein, such optical signals are referred to as propagating at anglesgreater than a critical angle with respect to a surface. While suchcritical angles generally depend on a ratio of refractive indices, andas used herein an index of refraction of an optical support material andan index of refraction of air can be used to determine critical angles.

[0037] A representative optical transceiver 200 configured to transmitand receive optical signals is illustrated in FIG. 2. The transceiver200 includes a hologram 202 applied to a surface 204 of an opticalsupport 206. The hologram 202 is configured to direct or diffract aninput optical beam 208 to a reflective surface 210. The reflectivesurface 210 is illustrated for convenience as a spherical surface butthe reflective surface 210 typically corresponds to an off-axis sectionof a parabola and is configured to direct a diffracted optical beam 212to converge at or near a surface 214. Other shapes can be used for thesurface 210 such as on- or off-axis parabolic, elliptical, hyperbolic,spherical, aspheric, or toric sections. Optical power can also beprovided by the hologram 202. To enhance reflectivity, the surface 210can be coated with a reflective coating such as a metallic coating ofaluminum, silver, gold, nickel, chromium, rhodium, or a combination ofthese or other metals. Dielectric coatings can also be used such asmultilayer coatings that include alternating layers of high and lowrefractive index materials. Alternatively, a hologram can be provided.

[0038] The optical support 206 can be made of various optical materialsincluding plastic optical materials such as acrylics, polycarbonates,optical glasses, fused silica, and other optical materials. The opticalmaterial is generally selected based on considerations such as cost andoptical properties such as transmittance in a wavelength range overwhich a transceiver is to be used. A wavelength range in which opticalcommunication components are readily available is between about 500 nmand about 1700 nm, but other wavelengths can be used. In someapplications, wavelength ranges are selected based on eye safetyconsiderations or on building window transmittances. Surfaces of theoptical support 206 such as the surface 210 and the surface 214 can beformed by polishing, molding processes such as injection molding,casting, machining or other process. In addition, such surfaces can bedefined by additional optical elements that are attached to the opticalsupport 206 by, for example, an optical epoxy or other adhesive. As aspecific example, a flat optical surface can be provided by attachmentof an optical window or other optically flat substrate to the opticalsupport. By providing optical surfaces on the optical support 206, amechanically and optically robust transceiver configuration is obtained.

[0039] As shown in FIG. 2, the diffracted beam 212 is produced by thehologram 202 but other optical elements can be used instead of thehologram 202. For example, replica diffraction gratings or ruleddiffraction gratings can be used, and such gratings can be blazed forimproved diffraction efficiency. Ronchi rulings can be used as well, andoptical power can be included in the hologram 202 so that some focusingof the diffracted beam 212 is produced. As used herein, a hologramrefers to a recorded optical interference pattern, and can be configuredfor use in reflection or in transmission.

[0040] The diffracted optical beam 212 is converged by the surface 210and delivered to an optical fiber module 216 situated at the surface214. According to the example of FIG. 2, the optical fiber module 216includes a fiber connector bulkhead adapter 217 that receives an opticalfiber 218 so that the converged optical signal is delivered to theoptical fiber 218. Typically, an end of the optical fiber 218 isconnectorized for attachment to the bulkhead adapter 217, and in aspecific example, the fiber 218 is provided with a so-called FC typeconnector and the bulkhead adapter 217 is an FC adapter.

[0041] The optical transceiver 200 is configured for transmission andreception of optical signals. An optical signal can be delivered by theoptical fiber 218 to the surface 210 and to the surface 204 andoutwardly directed by the hologram 202. Thus, the optical transceivercan server either as a transmitting transceiver or a receivingtransceiver.

[0042] A surface 220 of the optical support 206 is configured to benon-parallel with respect to the surface 204. Providing a relative tiltbetween these surfaces reduces the magnitude of optical signals thatexperience one or more reflections by the surfaces 204, 220 or othersurfaces that are undesirably delivered to optical receiver modules. Inaddition, to reduce unwanted optical signals, portions of the surfaces204, 210, 214, 220, and other surfaces can be provided with absorbing oranti-reflection optical coatings. Such coatings can be configured toabsorb or reduce reflections at wavelengths associated with stray light.As shown in FIG. 2, the surface 220 is configured so that the opticalsupport 206 tapers toward the surface 214, but in other examples thesurface 220 can be configured so that the optical support tapers towardthe surface 210.

[0043] The hologram 202 is configured to direct selected optical signalsto the surface 210 and to permit unselected optical radiation topropagate towards the surface 220. Such unselected signals can beabsorbed with an absorbing coating situated on the surface 220 or thesurface 220 can be provided with an antireflection coating to increasethe portion of the unselected radiation that exits the transceiver 206.In addition, as shown in FIG. 2, the hologram 202 is configured todirect signal light at a wavelength of about 783 nm at an angle of about36.2 degrees with respect to a line perpendicular to the surface 204.For this angle, a hologram thickness of about 20 μm is selected toreduce polarization dependence of the diffraction efficiency of thehologram 202. (Hologram diffraction efficiency is generally a functionof light polarization direction with respect to the fringe directionrecorded in the hologram.) The diffracted optical signal 212 canpropagate within the optical support 206 at an angle with respect to thesurface 204 that is greater than the critical angle. Thus, stray lightcan accompany the diffracted optical signal only if diffracted by thehologram 202. Generally the hologram 202 is configured to diffract onlyselected wavelengths (and not wavelengths associated with stray light orbackground light), so that little unwanted light accompanies the desiredsignal light. In particular, the hologram 202 can appear clear or highlytransmissive at some wavelengths and have a high diffraction efficiencyat a selected communication wavelength. Because the desired signal lightis generally received through a small aperture (such as a core of amultimode fiber or a single mode fiber), non-signal wavelengths that arediffracted at other angles are not efficiently coupled for detection ortransmission.

[0044] With reference to FIG. 3, an optical transceiver 300 includes ahologram 302 or other light directing element situated at or bonded to asurface 304 of an optical support 306. The optical transceiver 300 isconfigured to receive an optical signal 308 through the hologram 302,and to direct a diffracted or otherwise deflected portion 312 of theoptical signal to a surface 310 and to a surface 309. The opticalsupport 306 includes a first portion 314 and a second portion 316 thatare bonded at an interface surface 318. A surface 320 is configured toreduce multiple reflections within the optical support 306 and directany such reflected light away from a collection region 322.

[0045] With reference to FIG. 4, an optical transceiver 400 includes ahologram 402 configured to direct a portion 412 of an input opticalsignal 408 toward a first curved surface 410 and a second curved surface411. The surfaces 410, 411 are selected to converge the portion 412 ator near a surface 414. As shown in FIG. 4, an optical support 406includes two surfaces (the surfaces 410, 411) that have optical powerand serve to converge or otherwise focus the signal portion 412.

[0046] With reference to FIG. 5, an optical transceiver 500 includes ahologram 502 that is configured to direct a diffracted portion 512 of aninput optical signal 508 to a planar surface 510 and to a curved surface511 that is configured to converge the diffracted portion 512, typicallyat or near a surface 509. The surfaces 510, 511 are convenientlyprovided on an optical support 506, but the optical support 506 can beconfigured as two or more pieces bonded together. In addition, an unusedportion 519 of the optical support 506 can be removed.

[0047] Additional illustrative embodiments are illustrated in FIGS. 6-7.Referring to FIG. 6, a transceiver 600 includes a Ronchi ruling 602configured to direct an optical signal portion 612 of an input opticalsignal 608 to a curved surface 610 and to an output surface 614 of anoptical support 606. A rear surface 611 is arranged approximatelyparallel to a front surface 604. The shape or curvature of the curvedsurface 610 is selected to converge the optical signal portion 612.

[0048] Referring to FIG. 7, an optical transceiver 700 includes a firstsurface 704 that supports a hologram 702 that is configured to direct asignal portion 712 to a curved surface 710. The curved surface 710 isselected to converge the signal portion 712 and to direct the signalportion 712 to a surface 714 that reflects the signal portion 712 backto the surface 710. As shown in FIG. 7, the signal portion 712 convergesat or near the surface 710 at a location 717 and can be collected by anoptical system or an optical fiber and delivered to an electrical systemfor conversion into an electrical signal.

[0049] Several example optical transceivers are described above withreference to receiving optical signals. These example transceivers alsoserve as transmitters in which a converged optical signal is processedor collimated by one or more curved surfaces and then directed along anoutput direction by a hologram or other optical element. In additionalexamples, optical transceivers are configured so that diffracted ordeflected optical signal portions are reflected by one or more surfaces,and can be reflected by a single surface one or more times. In otheralternative examples, two holograms are attached to a single opticalsupport so that one is used for transmission and the other is used forreception. In such examples, separate optical fibers can be provided fordelivering optical signal to the transceivers and obtaining opticalsignals from the transceivers.

[0050] An arrangement for recording a hologram for use in the opticaltransceivers described above is illustrated in FIG. 8. Spatiallyfiltered optical beams 802, 804 are directed to a surface 806 of a prism808. The optical beams interfere at a holographic recording element 810situated at a surface 811 of the prism 808. The holographic recordingelement 810 typically includes a photosensitive layer and a transparentsupport layer. Alternatively, a photosensitive layer can be applieddirectly to the surface 811. The holographic recording element is placedon the surface 811 and reflections by the holographic recording element810 are reduced by index matching to the surface 811 with, for example,an index-matching liquid. A rectangular prism 812 is placed on theholographic recording element 810 and index matched. A back surface 814of the rectangular prism 812 is coated with an absorbing coating toreduce reflections.

[0051] Optical transceivers are typically configured for use withoptical signals in wavelength ranges for which common holographicrecording materials are not the most sensitive. Accordingly, hologramrecording is configured based on the difference in recording wavelengthand playback wavelength. In a representative example, the recordingwavelength is a wavelength associated with an argon ion laser (forexample, 488 nm or 514.5 nm) and the playback wavelength is about 785nm. Non-standard holographic materials that are more sensitive atplayback wavelengths can also be used. In some examples, holograms suchas the hologram 202 are recorded using HRF-600-X113-6*0.5 photopolymeravailable from DuPont Corporation, Wilmington, Del. In addition,shrinkage of holographic materials can be compensated and as notedabove, a thickness of a holographic recording material can be selectedto reduce polarization dependence of hologram diffraction efficiency.Index of refraction modulation in a hologram can be associated withpolarization dependence of diffraction efficiency, and selection of anindex modulation permits control of polarization dependence. Suchholographic configurations are described in, for example, H. Kogelnik,“Coupled Wave Theory for Thick Holograms,” Bell Sys. Tech. J.48:2909-2947 (1969), which is incorporated herein by reference.

[0052] A mounted optical transceiver 900 is illustrated in FIG. 9. Thetransceiver 900 includes an optical support 902 and a mirror section 903that is attached to the optical support 902 and that defines areflecting surface for input/output optical signals. Optical signals aredelivered to the optical transceiver 900 at a fiber connector adapter910. The transceiver 900 is aligned with alignment mounts 904, 906, 908that include respective adjustment mechanisms 920, 922, 924 and surfacemounting portions 930, 932, 934. The surface mounting portions 930, 932,934 are configured for mounting to various surfaces such as a officewindow using an adhesive, an adhesive pad, or other method. Theadjustment mechanisms 920, 922, 924 are attached to the optical support902 with an adhesive. Alternatively, mounting holes, surfaces, tabs, orother features can be provided as part of the optical support 902,particularly for plastic optical supports. Mounts for opticaltransceivers are preferably configured for compactness, ease ofinstallation, and to be unobtrusive after installation and thearrangement of FIG. 9 permits easy installation and alignment.

[0053]FIGS. 10A-10B are schematic diagrams illustrating alignment andmounting mechanisms suitable for use in the apparatus of FIG. 9.Referring to FIG. 10A, an alignment mechanism 1000 includes a grooveplate 1006 configured to be bonded with an adhesive layer 1004 to awindow 1002. A groove 1007 is defined in the groove plate 1006 and isconfigured to receive an adjustment screw 1008 of an adjustment plate1009. A spring 1011 or the like is situated to urge the adjustment plate1009 toward the groove plate 1006 so that the adjustment screw 1008contacts the groove plate 1006. A surface 1016 of the adjustment plate1009 is configured for mounting to an optical transceiver.

[0054] Referring to FIG. 10B, an alignment mechanism 1020 includes aslot plate 1026 configured to be bonded with an adhesive layer 1024 to awindow 1022. A slot 1027 is defined in the plate 1026 and is configuredto receive an adjustment screw 1028 of an adjustment plate 1029. Aspring 1031 or the like is situated to urge the adjustment plate 1029toward the plate 1026 so that the adjustment screw 1028 contacts theplate 1026. A surface 1030 of the adjustment plate 1029 is configuredfor mounting to an optical transceiver.

[0055] The alignment mechanisms of FIGS. 10A-10B are based on so-calledkinematic mounts, but other alignment mechanisms can be based on flexuremounts or gimbal mounts. Such mechanisms can be provided individuallyfor attachment to an optical transceiver and to a window through which atransceiver is to send or receive optical signals. Using such mountspermits an optical transceiver at a selected location to be configuredto communicate with an optical transceiver at another location.

[0056] With reference to FIG. 11, an optical transceiver 1100 isattached to a first window 1102 and is configured to send and receiveoptical signals through the first window 1102 and a second window 1104along a path defined by ray directions 1106, 1107. The opticaltransceiver 1100 includes an optical support 1110 and a hologram 1112.An input optical signal propagates through the windows 1102, 1104, theoptical support 1110, and the hologram 1112 and is reflected by asteering mirror 1114 back to the hologram 1112. The mirror is configuredto be rotatable about gimbals 1116 and in one embodiment is immersed inan index-matching material 1118 such as an index-matching liquid that isretained by a container 1120. A curved reflective surface 1122 isprovided on the optical support 1110, and typically corresponds to anoff-axis section of a parabola. The input optical signal received by thetransceiver. 1100 is directed to the steering mirror 1114 that isaligned with the gimbals 1116 so that a diffracted portion of thereflected optical signal is directed to the parabolic mirror 1122 andconverged to an output 1124. By adjustment of the steering mirror 1114,optical signals from a variety of remote locations can be detected.Similarly, an optical signal applied to the output 1124 can be deliveredto a selected remote location by adjustment of the steering mirror 1114.The mirror can also be configured to be steered about with, for example,a set of mutually orthogonal gimbals for two dimensional coverage.

[0057] An example optical transceiver 1200 using a reflective hologram1202 is illustrated in FIG. 12. The hologram 1202 is attached to asurface 1206 of an optical support 1207 and is configured to direct atleast a portion 1212 of an input optical signal 1208 to a curvedreflective surface 1210 and to a coupling surface 1209. As shown in FIG.12, a surface 1220 through which optical signals enter and/or exit theoptical support 1207 is tilted with respect to the surface 1206. Forconvenience, refraction of the input optical signal 1208 at the surface1220 is not shown but the optical signal 1208 need not enter the opticalsupport 1208 perpendicularly to the surface 1220. The hologram 1202 istypically configured to deflect optical signals of selected wavelengthsto the curved reflective surface 1210 and transmit other wavelengths. Inaddition, the deflected optical signal portion 1212 typically propagatesat an angle greater than a critical angle with respect to the surface1206.

[0058] An optical transceiver 1300 illustrated in FIG. 13 includes ahologram 1302 situated on a curved surface 1305 of an optical support1306. The hologram 1302 is configured to deflect a portion 1312 of aninput optical beam 1308 to a reflective surface 1310 and to couplingsurface 1309. As shown in FIG. 13, an optical beam 1318 associated with,for example, vision through the optical transceiver 1300 with opticalradiation at wavelengths transmitted by the hologram 1302.

[0059] With reference to FIG. 14, an optical transceiver 1400 includesholograms 1402, 1410 situated at respective surfaces 1403, 1411 of anoptical support 1406. The hologram 1402 is configured to direct aportion 1412 of the optical beam 1408 to the hologram 1410 thatconverges or partially converges the portion 1412 at, near, or through acoupling surface 1414. The optical transceiver 1400 does not includecurved optical surfaces that provide optical power but instead includesthe hologram 1410. While the hologram 1402 can be configured to directthe optical beam 1408 to the surface 1411 as well as converge theoptical beam 1408, providing two holograms simplifies hologramfabrication.

[0060] With reference to FIG. 15, an optical transceiver 1500 isretained by a pointing assembly 1502 that is configured to directoptical signals to or receive optical signals from a selected location.The optical transceiver 1500 includes an optical support 1504 having aninput/output surface 1506 and a focusing surface 1508. A transmithologram and a receive hologram can be provided on the surface 1506, ora single hologram can be used. The transmit hologram directs an opticalsignal from a prism portion 1510 to a portion 1508 a of the focusingsurface 1508 and that is then transmitted through the surface 1506.Received optical signals are directed by an input hologram to a portion1508 b of the focusing surface 1508 and then directed to the prismportion 1510. The portions 1508 a, 1508 b are typically independentlyconfigured to direct, focus, or otherwise process received andtransmitted optical signals. Optical signals can be coupled into and outof the optical support 1504 at a coupling surface 1516 with a reflectiveprism surface 1520. An additional prism portion 1512 can be providedhaving an input/output surface 1514 and a reflective surface 1518, sothat optical inputs and outputs can be associated with different prismportions.

[0061] The pointing assembly 1502 includes adjustment mechanisms 1530,1532, 1534 so that the optical transceiver 1500 can be configured tosend and/or receive optical signals from a selected location. Theadjustment mechanisms 1530, 1532 include fixed portions 1542, 1544 thatare fixed with respect to the optical support 1504, and referenceportions 1546, 1548 that are configured for attachment to a mountingsurface such as, for example, a window. The adjustment mechanism 1534can be similarly configured.

[0062] With reference to FIG. 16, an optical transceiver 1600 isretained by a pointing assembly 1602 that is configured to directoptical signals to or receive optical signals from a selected location.The optical transceiver 1600 includes an optical support 1604 having aninput/output surface 1606 and a focusing surface 1608. A transmithologram and a receive hologram can be provided on the surface 1606, ora single hologram can be used. The transmit hologram directs an opticalsignal that is directed from a transmit portion 1610 of a couplingsurface 1609 to the surface 1608 and that is then transmitted throughthe surface 1606. Received optical signals are directed by the receivehologram to the focusing surface 1608 and then directed to a portion1612 of the coupling surface 1609.

[0063] The pointing assembly 1602 includes adjustment mechanisms 1630,1632, 1634 so that the optical transceiver 1600 can be configured tosend and/or receive optical signals from a selected location. Theadjustment mechanisms 1630, 1632 include fixed portions 1642, 1644 thatare fixed with respect to the optical support 1604, and referenceportions 1646, 1648 that are configured for attachment to a mountingsurface such as, for example, a window. The adjustment mechanism 1634can be similarly configured. In representative examples, fixed portionsand reference portions are urged toward each other using springs ormagnets attached to one or both of the fixed and reference portions.

[0064] With reference to FIG. 17, an optical transceiver 1700 includes adiffractive optical element (DOE) 1702 or other light directing elementsituated at or bonded to a surface 1704 of an optical support 1706. Theoptical transceiver 1700 is configured to receive an optical signal 1708through windows 1710, 1712 that are separated by an air gap 1711. Asshown in FIG. 17, a surface 1705 of the optical support 1706 is attachedto a surface 1713 of the window 1712. In other examples, the opticalsupport 1706 is index matched to the window 1712 with an index-matchingmaterial and is retained at the window 1712 with supports that are notshown in FIG. 17. The optical signal 1708 is transmitted to the DOE 1702and a mirror 1716 or other reflective surface that is aligned withgimbals 1730 so that a diffracted portion 1715 of the reflected opticalbeam is directed to a reflective region 1717 of the surface 1705 and toan input/output surface 1718 of the optical support 1706. The region1717 is configured to reflect the diffracted portion 1715 of the opticalbeam 1708 to the surface 1718. Typically, the reflective region 1717 isprovided with a reflective coating such as a metallic or dielectriccoating, or a space can be provided between a surface 1720 and thesurface 1713 so that the diffracted portion 1715 is substantiallyreflected by, for example, total internal reflection. If the reflectiveregion 1717 is provided with a reflective coating, it may be convenientto designate a portion of the surface 1704 as an input/output surface.Typically, optical signals are received from or delivered to the opticaltransceiver 1700 with a segment 1722 of an optical fiber, and an opticalbeam shape is selected using an optical module 1723 that includescollimating, focusing, or defocusing optics that are generally selectedin conjunction with optical power provided in the DOE 1702. Indexmatching is accomplished with a container 1724 that is configured toretain an index-matching material 1725 such as mineral oil or otherindex-matching material. Gimbals 1730 are provided for orienting themirror 1716 for transmission to or reception from a predeterminedlocation. Gimbals for single-axis rotation are shown in FIG. 17, butgimbals for rotation about two or more axes can be provided.

[0065] The optical transceiver 1700 is described above with reference toreception of an incoming optical signal, but can also serve to transmitan optical signal received at the input/output surface 1718. As shown inFIG. 17, surfaces of the optical support 1706 are generally planar, butin additional examples, optical power can be provided at one or moresurfaces, and transceivers can be configured so that input or outputoptical beams are reflected and/or focused/defocused at one or moresurfaces. In additional examples, a planar or curved mirror or otheroptical element is adjustable with a kinematic mount, a flexure mount,or other adjustment mechanism. Such reflecting optical elements can beadjusted with respect to one or more axes of rotation to selecttransmission or reception directions.

[0066] With reference to FIG. 18, an optical transceiver 1800 includes adiffractive optical element (DOE) 1802 bonded to a surface 1804 of anoptical support 1806. The optical transceiver 1800 is configured toreceive an optical signal 1808 through windows 1810, 1812 that areseparated by an air gap 1811. As shown in FIG. 18, a surface 1805 of theoptical support 1806 is attached to a surface 1813 of the window 1812.The optical beam 1808 is transmitted to the DOE 1802 and a curved mirror1816 that is aligned with gimbals 1830 so that a diffracted portion 1815of the reflected optical beam is directed to a reflective region 1817 ofthe surface 1805 and to an input/output surface 1818 of the opticalsupport 1806. The region 1817 is configured to reflect the diffractedportion 1815 of the optical beam 1808 to the surface 1818. Opticalsignals are received from or delivered to the optical transceiver 1800with a segment 1822 of an optical fiber and optical beam shape isselected using an optical module 1823 that includes collimating,focusing, or defocusing optics that are generally selected inconjunction with optical power provided in the DOE 1802 and the curvedmirror 1816. Index matching is accomplished with a container 1824 thatis configured to retain an index-matching material 1825 such as mineraloil or other index-matching material. Gimbals 1830 are provided fororienting the mirror 1816 for transmission to or reception from apredetermined location. An adjustment screw 1850 and a spring 1852 areprovided for selecting an angle of rotation of the mirror 1816, butother adjustment mechanisms such as flexures can be used. Adjustmentscan be mechanized, and can be based on, for example, detected opticalsignal power. As shown in FIG. 18, the screw 1850 and the spring 1852contact the mirror 1816 directly, but generally the mirror 1816 isattached to a mounting plate, mirror mount, or other mounting assembly,and adjustment mechanisms directly contact the mounting plate but notthe mirror 1816.

[0067] An example optical transceiver 1900 using a reflective hologram1902 is illustrated in FIG. 19. The hologram 1902 is attached to arotational mount 1921 and is surrounded by an index-matching liquid 1922that is contained by an enclosure 1924. At least a portion 1912 of aninput optical signal 1908 is directed to an optical support 1907 thatincludes a curved reflective surface 1910 and a coupling surface 1909.As shown in FIG. 19, a surface 1920 through which optical signals enterand/or exit the optical support 1907 is tilted with respect to thesurface 1906. For convenience, refraction of the input optical signal1908 at the surface 1920 is not shown in FIG. 19, but the optical signal1908 need not enter the optical support 1908 perpendicularly to thesurface 1920. The hologram 1902 is typically configured to deflectoptical signals of selected wavelengths to the curved reflective surface1910 and transmit other wavelengths. In addition, the deflected opticalsignal portion 1912 typically propagates at an angle greater than acritical angle with respect to the surface 1906. An angle of rotation ofthe hologram 1902 can be adjusted with the rotational mount 1921 fortransmission to or reception from a selected location. In otherexamples, a hologram can be provided on the surface 1906 and a mirrorprovided for rotational adjustment.

[0068] With reference to FIG. 20, an optical transceiver 2000 includes ahologram 2002 or other light directing element situated at or bonded toa surface 2004 of a window 2005. The optical transceiver 2000 isconfigured to receive an optical signal 2008 through the hologram 2002,and to direct a diffracted or otherwise deflected portion 2012 of theoptical signal to surfaces 2009, 2010 of an optical support 2006. Theoptical support 2006 includes a first portion 2014 and a second portion2016 that are bonded at an interface surface 2018. A surface 2020 isconfigured to reduce multiple reflections within the optical support2006 and direct any such reflected light away from a collection region2022. One or more tilt angles of the optical support 2006 are selectablewith a gimbal mount 2030 or other mechanism. An enclosure 2032 isconfigured to retain an index-matching fluid 2034.

[0069] An example optical transceiver 2100 using a reflective hologram2102 is illustrated in FIG. 21. The hologram 2102 is configured todirect optical beams between an input surface 2120 and an interfacesurface 2109 using a reflector 2110 that is attached to a rotationalmount 2121 and is surrounded by an index-matching liquid 2122 that iscontained by an enclosure 2124. At least a portion 2112 of an inputoptical signal 2108 is directed to the reflector 2110. As shown in FIG.21, the surface 2120 through which optical signals enter and/or exit anoptical support 2107 is tilted with respect to a surface 2106. In atypical installation, the input surface 2120 is bonded to a window withan index matching material such as an optical adhesive, and reflectionsfrom the surface 2106 are substantially eliminated so surface tilt isunnecessary. The hologram 2102 is typically configured to deflectoptical signals of selected wavelengths to the reflector 2110. Thedeflected optical signal portion 2112 typically propagates at an anglegreater than a critical angle with respect to the surface 2106. An angleof rotation of the reflector 2110 can be adjusted with the rotationalmount 2121 for transmission to or reception from a selected location. Insome examples, the reflector 2110 is a holographic optical element, andcan include optical power for focusing, defocusing, or otherwisecontrolling optical beams.

[0070] Representative examples are described and it will be apparentthat these examples can be modified in arrangement and detail. Forexample, optical supports can include reflective or refractive opticalsurfaces defined by polished, molded, or machined surfaces of theoptical support, or by optical surfaces bonded to surfaces of an opticalsupport. A transceiver can be configured to transmit, receive, ortransmit and receive. Two or more diffractive elements can be providedon an optical support for transmission and reception, respectively. Acurved surface can be configured to receive and converge optical signalsfrom a receiver hologram and to deliver optical signals to a transmitterhologram. Such a curved surface can be configured so that received andtransmitted optical signals are directed to a first convergence regionand received from a second convergence region, respectively. Forexample, separate fiber cables can be used for received optical signalsand for optical signals to be transmitted. A transceiver can includerespective holograms for transmit and receive functions, and reflectiveand/or refractive surfaces can be formed that direct optical signals toand from the respective holograms. Rotations of diffractive opticalelements or reflective surfaces can be provided with gimbal mounts,flexures, kinematic mounts or otherwise provided. Various surfaces ofoptical transceivers can be configured to be rotatable. For example,surfaces 210, 2310, 410, 411 shown in FIGS. 2-4 can be rotatable, or anentire optical support can be rotatable. By providing an opticaltransceiver with rotatable surfaces, a transceiver can be fixedlyattached to, for example, an office window, and a communicationdirection selected by adjusting one or more rotatable surfaces. Inaddition, transceivers surfaces can be positioned on a window orotherwise positioned without alignment to a communication direction, androtatable surfaces adjusted to select the communication direction. Inview of these illustrative examples, we claim all that is encompassed bythe appended claims.

We claim:
 1. An optical transceiver, comprising: a diffractive opticalelement (DOE) configured to transmit an input optical beam; a reflectivesurface configured to receive the transmitted optical beam from the DOEand direct a reflected optical beam to the DOE; an optical detector; anda mount configured to rotate the reflective surface so that the DOEdiffracts at least a portion of the reflected optical beam to theoptical detector.
 2. The optical transceiver of claim 1, furthercomprising an index-matching material situated at the reflectivesurface.
 3. The optical transceiver of claim 2, wherein theindex-matching material extends from the reflective surface to the DOE.4. The optical transceiver of claim 1, further comprising an opticalsupport having a first surface configured to receive the diffractedportion of the reflected optical beam and to direct the diffractedportion to an output surface.
 5. The optical transceiver of claim 1,wherein the DOE is configured to diffract at least a portion of thereflected optical beam to an output surface.
 6. An optical transmitter,comprising: a diffractive optical element (DOE) configured to receive anoutput optical beam and diffract at least a portion of the outputoptical beam; a reflective surface configured to receive the diffractedportion of the output optical beam and direct a reflected portion to theDOE; and a mount configured to rotate the reflective surface and selectan orientation of the reflective surface, wherein the orientation of thereflective surface is associated with selection of a transmissiondirection.
 7. The optical transmitter of claim 6, further comprising anindex-matching material situated at the reflective surface.
 8. Theoptical transmitter of claim 7, wherein the index-matching materialextends from the reflective surface to the DOE.
 9. The opticaltransmitter of claim 6, further comprising an optical support having afirst surface configured to receive the output optical beam and todirect at least a portion of the output optical beam to the DOE.
 10. Theoptical transmitter of claim 6, wherein the DOE is configured todiffract at least a portion of the output optical beam received from thefirst surface of the optical support to the reflective surface.
 11. Anoptical transceiver, comprising: a diffractive optical element (DOE);and a reflective surface configured to receive an optical beam from theDOE and direct a reflected portion to the DOE, wherein the reflectivesurface is rotatable with respect to the DOE.
 12. The opticaltransceiver of claim 11, wherein the DOE is bonded to an opticalsupport.
 13. The optical transceiver of claim 11, wherein the DOE isconfigured to direct the optical beam to an output surface of theoptical support based on a wavelength associated with the optical beam.14. The optical transceiver of claim 11, wherein the optical supportincludes at least one concave or convex surface.
 15. The opticaltransceiver of claim 13, wherein the optical support includes a surfaceconfigured to communicate the optical beam between the DOE and theoutput surface.
 16. The optical transceiver of claim 15, wherein thesurface of the optical support is configured to communicate the opticalbeam between the DOE and the output surface by total internalreflection.
 17. The optical transceiver of claim 13, wherein acommunication direction is selectable based on a rotation angle of thereflective surface with respect to the DOE.
 18. An optical transceiver,comprising: an optical support having a first surface configured to besituated adjacent a window, a second surface, and a coupling surface; adiffractive optical element (DOE) situated adjacent the second surface;a reflective optical surface; and an optical mount adjustable to selectan orientation of the reflective optical surface with respect to thatDOE so that the DOE and the reflective optical surface direct a lightflux from the first surface to the coupling surface, or direct a lightflux from the coupling surface to the first surface.
 19. The opticaltransceiver of claim 18, further comprising an index-matching fluidsituated to reduce reflections of a light flux at the second surface.20. The optical transceiver of claim 19, wherein the first surfacecomprises a reflective region configured to direct a light flux to thecoupling surface or to the DOE.
 21. The optical transceiver of claim 20,wherein the reflective region includes a reflective coating.
 22. Theoptical transceiver of claim 21, wherein the reflective region isconfigured to provide total internal reflection.
 23. A network,comprising: at least two computer devices; and an optical transceiver asrecited in claim 18 and configured to interconnect the at least twocomputer devices.
 24. A communication method, comprising: receiving anoptical signal beam; directing the optical signal beam to a diffractiveoptical element (DOE); and reflecting at least a portion of the opticalsignal beam received from the DOE back to the DOE; and diffracting aportion of the optical signal beam received from the reflective surfacewith the DOE so that the diffracted portion is directed to an opticaldetector.
 25. The communication method of claim 24, further comprisingselecting a communication direction based on a rotation angle of thereflective surface with respect to the DOE.
 26. The communication methodof claim 25, wherein the step of selecting a communication directionincludes adjusting the orientation angle of the reflective surface withrespect to the communication direction.
 27. The communication method ofclaim 26, further comprising directing the diffracted portion to theoptical detector based on a wavelength associated with the opticalsignal beam.
 28. A method of processing an optical signal, comprising:directing the optical signal to a diffractive optical element (DOE);receiving the optical signal from the DOE and adjusting an angle ofreflection of the optical signal; and diffracting at least a portion ofthe optical signal reflected to the DOE to a surface of an opticalsupport so that the portion propagates in the optical support at anangle greater than a critical angle with respect to the surface.
 29. Themethod of claim 28, further comprising directing the optical signal to asurface of the optical support having optical power.
 30. The method ofclaim 29, wherein the optical power of the surface is based on a surfacecurvature.